The freshwater i was considering are african cichids, angelfish, discus, loaches, ect. However a friend of mine runs the local fish store and she said she would help me with a salt tank. She said that they aren't that much harder because the live rock and sand help with filtration and stuff as long as you cycle it properly. However I do think i'm going to find something other than the eel since it will eat any cleaners i put in the tank. I like the puffers but i would run into the same problem so i'm still working on the line up. At least i have about 2 months to decide. Right now i just have to hurry and decide on fresh or salt. I know i need a filter for either, but do fresh tanks use powerheads too? I've never done a larger than 20 gal tank. Will the extra oxygen help or just stress the fish?